AMD's Radeon HD 5670 graphics card

With its DirectX 11 graphics cards now populating the middle and upper echelons of the marketand last year's supply issues largely behind itAMD is now proceeding into the low-end arena. Today, we're getting to see the first product of that expansion: the Radeon HD 5670, which should start cropping up in e-tail stocks soon for about $99.

To keep the price tag in the double digits, AMD has taken the world's smallest scalpel and carefully sliced away some of the pixel-crunching resources from the bigger and more powerful GPUs in Radeon HD 5700, 5800, and 5900-series cards. That means the newcomer follows a similar recipe to the rest of its brethren, delivering DirectX 11 support and multi-display capabilities in a freshly minted 40-nm chip. You're just getting it in a smaller, fun-sized portion.

Is fun-sized still tasty, or has AMD removed too much of the icing compared to other DX11 Radeons? That's what we're about to find out.

The ents are going to war!
AMD has nicknamed the Radeon HD 5670's GPU "Redwood," keeping with the coniferous naming scheme of its DirectX 11 Evergreen family. Under the hood (or bark, rather), Redwood contains half the execution resources of Juniper, the GPU in Radeon HD 5700-series cards, with the same 128-bit memory interface. Seeing as Juniper itself has half the execution resources and half the memory interface width of the Cypress chip that powers 5800- and 5900-series offerings, one could say Redwood is a quarter Cypress with a double-wide memory interface. But that'd be oversimplifying things just a tad. Here's a human-readable overview of Redwood's guts:

A block diagram of Redwood. Source: AMD.

Let's see... We have five SIMD units, each containing 80 ALUs and tied to one texture unit capable of sampling and filtering four texels per clock. That gives us 400 ALUs (or stream processors) and 20 texels/clock, down from 800 SPs and 40 texels/clock on the Radeon HD 5770. AMD has also removed two of the ROP units, leaving Redwood capable of cranking out eight pixels each clock cyclehalf as many as the 5770. Again, though, both the 5670 and its bigger brother have the same memory interface setup: 128 bits wide and compatible with 4Gbps GDDR5 memory.

All of this hedge trimming has left AMD with a small (we'll look at die sizes soon), cheap-to-manufacture GPU that's also quite power-efficient. According to AMD, the 5670 will draw just 14W at idle and 61W under a typical load. That means no PCI Express power connectors and hopefully low noise levels, despite the spartan-looking single-slot cooler.

Otherwise, as far as we can tell, Redwood has the same DirectX 11 capabilities and hardware features as Juniper. AMD advertises Eyefinity support, too, but the maximum number of supported displays is limited to four, and the reference card will only connect up to three displays.

The Radeon HD 5670 is but the first member of a whole budget DX11 lineup from AMD. For users with really tight budgets, the company plans to follow up in February with the Radeon HD 5500 and 5400 series. The former will cram Redwood chips and 128-bit memory interfaces into sub-50W thermal envelopes, while the 5400 series will be based on the Cedar GPU, whose memory interface is only 64 bits wide. AMD tells us the Radeon HD 5450 will have a low-profile form factor and enough brawn to run Tom Clancy's H.A.W.X. on a three-display setup.

Considering the recent supply problems AMD has faced because of poor 40-nm yields at TSMC, one might be rightfully concerned about the availability of these products. We brought the subject up with AMD, which replied that it expects "multiple tens of thousands" of Radeon HD 5670 units to be available for the launch, followed by "similar quantities every week." New 40-nm Radeons are seeing massive demand, AMD added, but 40-nm supply is now meeting the company's expectations.